tl;dr: daughter almost drowned at swim team practice, how do I approach the coach?

Last night was my daughter's first night of swim team practice. This is the 6 and under group so they know the kids can't swim well and they have never seen any of these kids before. My daughter was late and hopped in the pool for the last lap. The instructor let her go (for a full length lap) and then stopped watching. About halfway across the pool, my daughter started showing signs of struggle (former lifeguard, I know the signs of struggle/drowning). Finally, just as I was about to jump in the damn pool fully dressed) another instructor grabbed her.

That night, she told me she couldn't yell for help because she was bobbing and getting air. We talked it through a lot and she told me all of her feelings during that time. I was impressed she told me she was not just scared but also mad that no one was helping her!

Tonight is our next practice. How do I approach this with the coach? I don't want to sound whiny or high and mighty "I was a lifeguard 20 years ago, blah blah blah". Help me find the right words?